Liquid crystal display device

ABSTRACT

A liquid crystal display device according to an embodiment of the present invention includes: a wiring substrate; an opposing substrate opposite to the wiring substrate; a sealing member for bonding the wiring substrate to the opposing substrate; a liquid crystal filled in a space defined by the wiring substrate, the opposing substrate, and the sealing member; a plurality of scanning signal lines formed in a display area formed inside the sealing member; a plurality of a display signal lines formed in the display area and crossing the scanning signal lines with an insulating film interposed therebetween; and a common signal line formed outside the display area, the scanning signal lines, the scanning signal lines, and common signal line being formed on the wiring substrate, and the common signal line including at least two conductive layers with one of the conductive layers changing a pattern width below a pattern of the sealing member.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a Divisional of U.S. Ser. No. 11/420,154, filed May24, 2006, the entire content of which is incorporated herewith byreference, and claims priority under 35 U.S.C. 119 to JapaneseApplication JP 2005-229329 filed Aug. 8, 2005.

BACKGROUND OF THE INVENTION Field of the Invention

In general, liquid crystal display devices are structured such that apair of upper and lower electrode substrates having transparentelectrodes are bonded to each other by use of a sealing member formedaround an image display portion of the substrate and liquid crystal isfilled therein. The liquid crystal display devices are classified intoan active matrix type and a passive matrix type. An active matrix typeliquid crystal display device as disclosed in Japanese Unexamined PatentApplication Publication No. 11-149087 has a TFT array substrate wherethin film transistors as switching elements are arranged in matrix (seeJapanese Unexamined Patent Application Publication No. 11-149087). Then,the TFT array substrate is bonded to an opposing substrate through asealing member. Liquid crystal is filled in between the TFT arraysubstrate and the opposing substrate.

FIG. 13 is a plan view showing a corner portion of a peripheral portionof an image display portion of the TFT array substrate constituting theliquid crystal display device as disclosed in Japanese Unexamined PatentApplication Publication No. 11-149087. In FIG. 13, reference numeral 1denotes a wiring substrate having a TFT array; 2, a display area; 3, ascanning signal line; 5, a display signal line; 7, a common signal line;and 8, a sealing member.

In the liquid crystal display device, the sealing member 8 is formedaround the display area 2. A pattern of the sealing member 8 has aportion overlapping with the scanning signal line 3 and a portionoverlapping with the display signal line 5. Further, the sealing member8 is arranged to overlap with the common signal line 7 at the corner ofthe display area 2. Assuming that the common signal line 7 is notprovided, a base portion on which the sealing member 8 is to be formedbecomes uneven: there is a step corresponding to the line height betweena portion having the scanning signal line 3 or the display signal line 5or the rest. Thus, a change in panel gap occurs due to the step at thecorner of the image display portion, and causes an uneven display.However, in the technique as disclosed in Japanese Unexamined PatentApplication Publication No. 11-149087, the common signal line 7 isformed near the corner of the wiring substrate 1 having the TFT arraythrough the same process as that of either the scanning signal line 3 orthe display signal line 5. As a result, a difference in level on thebase portion underlying the sealing member 8 on the array substrate iseliminated or reduced. Therefore, the uneven display due to the changein panel gap can be controlled.

On the other hand, in the passive matrix type liquid crystal displaydevice as disclosed in Japanese Unexamined Patent ApplicationPublication No. 2003-186041, a transparent substrate having a segmentelectrode for applying voltage to liquid crystal is bonded to anopposing substrate having a common electrode through a sealing member.Liquid crystal is filled in between the substrate and the opposingsubstrate. A pixel is defined as a crossing point between the segmentelectrode and the common electrode.

FIG. 14 shows the structure of the liquid crystal display device asdisclosed in FIG. 9 of Japanese Unexamined Patent ApplicationPublication No. 2003-186041. FIG. 14 is a sectional view showing thestructure of the liquid crystal display device. In FIG. 14, referencenumeral 101 denotes a transparent substrate provided with a segmentelectrode (not shown) for applying a voltage to liquid crystal; 7 a and7 b, a common signal line formed on the transparent substrate 101; 8, asealing member formed on the transparent substrate; 19, a commonelectrode applied with a common signal; 102, a transparent substrateprovided with the common electrode 19; 18, a conductive member; and 12,liquid crystal filled in a space defined by the above two substrates andthe sealing member.

A driving circuit (not shown) or flexible substrate (not shown) formedon the transparent substrate 101 supplies a common signal to the commonsignal line 7. The common signal supplied to the common signal line 7 isapplied to the common electrode 19 on the opposing substrate 102 throughthe conductive member 18. In this structure, the common signal linebelow the sealing member 8 has the two-layer structure, which enables alow line resistance. Further, the common signal line 7 is arranged tounderlie the sealing member 8, so the sealing member 8 blocksinfiltration of water from the outside of the panel to thereby improve acorrosion resistance of the common signal line 7.

however, the conventional liquid crystal display device has thefollowing problems. That is, in the liquid crystal display device ofFIG. 13, the common signal line 7 extends below the sealing member 8pattern. Hence, it is necessary to minimize a difference in level on thebase portion between a region where the sealing member 8 overlaps withthe common signal line and a region where the sealing member 8 overlapswith the scanning signal line 3 or the display signal line 5. In thisway, the abrupt change in panel gap that locally occurs can besuppressed. In general, it is rare that the scanning signal line and thedisplay signal line largely differ in film thickness. Thus, in theliquid crystal display device as disclose in Japanese Unexamined PatentApplication Publication No. 11-149087, the common signal line is formedusing a material for the scanning signal line or a signal line tothereby level the base portion below the sealing member 8 pattern. Thatis, if the film thickness of the common signal line 7 increases, anabrupt change in panel gap locally occurs. Accordingly, with thisstructure, the common signal line should be formed using one of thescanning signal line and the material for a signal line. It is difficultto lower the resistance of the common signal line.

Further, there is a method of increasing a pattern width of the commonsignal line to lower the line resistance. However, if the line patternwidth is increased, the width of a peripheral portion where the sealingmember 8 is formed is increased. As a result, a frame area increases,resulting in a problem in that a compact liquid crystal display devicewith a small panel size cannot be realized.

In addition, in the liquid crystal display device of FIG. 14, the commonsignal line 7 underlying the sealing member 8 pattern has the two-layerstructure, which realizes the low line resistance. However, if thecommon signal line of the two-layer structure is formed, there is apossibility that the height of the base portion largely changes at theborder between a region where the display signal line or scanning signalline overlaps with the sealing member 8 and a region where the commonsignal line overlaps with the sealing member. In this case, the unevendisplay is caused due to the abrupt change in panel gap at the portionconcerned. Accordingly, in the structure of FIG. 14, a region where thetwo-layer line can be formed is limited for avoiding the abrupt changein panel gap. In some cases, this hinders the reduction in resistancenecessary for high-speed driving.

As mentioned above, in the conventional liquid crystal display device,the uneven display is caused due to the abrupt change in panel gap, sothe resistance of common signal line cannot be lowered. That is, if thecommon signal line has the two-layer structure, the panel gap abruptlychanges. This leads to a problem in that the uneven display is caused,and display quality cannot be improved.

As discussed above, a conventional display device faces a problem inthat, if the resistance of the common signal line is lowered, the unevendisplay is caused due to the abrupt change in panel gap, and the displayquality cannot be improved.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of the aboveproblems, and it is accordingly an object of the invention to provide aliquid crystal display device that enables high display quality.

A liquid crystal display device according to a first aspect of theinvention includes: a wiring substrate; an opposing substrate oppositeto the wiring substrate; a sealing member for bonding the wiringsubstrate to the opposing substrate; a liquid crystal filled in a spacedefined by the wiring substrate, the opposing substrate, and the sealingmember; a plurality of scanning signal lines formed in a display areaformed inside the sealing member; a plurality of display signal linesformed in the display area and crossing the scanning signal linesthrough an insulating film; and a common signal line formed outside thedisplay area, the scanning signal lines, the scanning signal lines, andcommon signal line being formed on the wiring substrate, and the commonsignal line including at least two conductive layers with one of theconductive layers changing a pattern width below a pattern of thesealing member. Thus, a resistance of the common signal line can belowered with no abrupt change in panel gap, making it possible toimprove display quality.

According to a second aspect of the invention, in the liquid crystaldisplay device according to the first aspect, the common signal linebelow the pattern of the sealing member extends along one side of thesealing member, and the pattern width of the conductive layer is changedin a direction in which the common signal line extends. Thus, a delay ofa common signal can be suppressed.

According to a third aspect of the invention, in the liquid crystaldisplay device according to the second aspect, in the direction in whichthe common signal line extends, the pattern width of the conductivelayer increases as a distance from an end portion on a signal supplyside of the wiring substrate on which a signal is supplied to thedisplay signal line or the scanning signal line. Thus, an effectivepattern width of a common signal line can be increased, and a resistancecan be lowered.

According to a fourth aspect of the invention, in the liquid crystaldisplay device according to the second aspect, a plurality of lead-outlines for supplying a signal to the scanning signal line or the displaysignal line are provided outside the display area, and as the lead-outlines are connected with the scanning signal line or the display signalline, the pattern width of the common signal line is increased stepwise.Thus, an effective pattern width of a common signal line can beincreased, and a resistance can be lowered.

According to a fifth aspect, in the liquid crystal display deviceaccording to second aspect of the invention, at one side of the sealingmember where the common signal line extends, the common signal line isformed on the display area side inside the pattern of the sealingmember. Thus, an effective pattern width of a common signal line can beincreased, and a resistance can be lowered.

According to a sixth aspect, in the liquid crystal display deviceaccording to second aspect of the invention, among conductive layers ofthe common signal line, all the conductive layers but an uppermostconductive layer extend up to the outside of an outer edge of thepattern of the sealing member at one end of the sealing member in whichthe common signal line extends, and the conductive layers extending upto the outside of the outer edge of the pattern of the sealing memberare covered with two or more insulating films. Thus, corrosion of acommon signal line can be prevented.

According to a seventh aspect of the invention, in the liquid crystaldisplay device according to the first aspect, a plurality of lead-outlines for supplying a signal to the scanning signal line or the displaysignal line are provided outside the display area, a plurality of commonsignal auxiliary lines made up of conductive layers different from theconductive layers for the lead-out lines are formed between theplurality of lead-out lines, and a plurality of common signal lineconnecting lines connected with the plurality of common signal auxiliarylines are formed. This enables further reduction in resistance.

A liquid crystal display device according to an eight aspect of theinvention includes: a wiring substrate; an opposing substrate oppositeto the wiring substrate; a sealing member for bonding the wiringsubstrate to the opposing substrate; a liquid crystal filled in a spacedefined by the wiring substrate, the opposing substrate, and the sealingmember; a plurality of scanning signal lines formed in a display areaformed inside the sealing member; a plurality of display signal linesformed in the display area and crossing the scanning signal linesthrough an insulating film; and a common signal line formed outside thedisplay area and extending along one end of the sealing member below thepattern of the sealing member, the scanning signal lines, the scanningsignal lines, and common signal line being formed on the wiringsubstrate, and the common signal line including at least two conductivelayers, all the conductive layers but an uppermost conductive layeramong the conductive layers of the common signal line extending up tothe outside of an outer edge of the pattern of the sealing member at oneend of the sealing member in which the common signal line extends, andthe conductive layers extending up to the outside of the outer edge ofthe pattern of the sealing member being covered with two or moreinsulating films. Thus, a resistance of a common signal line can belowered, making it possible to improve display quality.

According to a ninth aspect of the invention, in the liquid crystaldisplay device according to the first aspect, the common signal lineincludes a conductive layer for forming the display signal line and aconductive layer for forming the scanning signal line. Thus, aresistance of a common signal line can be lowered, making it possible toimprove display quality.

According to a tenth aspect of the invention, in the liquid crystaldisplay device according to the eight aspect, the common signal lineincludes a conductive layer for forming the display signal line and aconductive layer for forming the scanning signal line. Thus, aresistance of a common signal line can be lowered, making it possible toimprove display quality.

A liquid crystal display device according to an eleventh aspect of theinvention includes: a wiring substrate; an opposing substrate oppositeto the wiring substrate; a sealing member for bonding the wiringsubstrate to the opposing substrate; a liquid crystal filled in a spacedefined by the wiring substrate, the opposing substrate, and the sealingmember; a plurality of scanning signal lines formed in a display areaformed inside the sealing member; a plurality of display signal linesformed in the display area and crossing the scanning signal linesthrough an insulating film; a plurality of lead-out lines for supplyinga signal to the display signal line or the scanning signal line, whichare provided outside the display area; a common signal line formedoutside the display area; a plurality of common signal auxiliary linesarranged between the adjacent lead-out lines and formed using aconductive layer different from the lead-out lines; and a common signalconnecting line for bringing the plurality of common signal auxiliarylines into conduction. Thus, a resistance of a common signal line can belowered, making it possible to improve display quality.

According to the present invention, it is possible to provide a liquidcrystal display device that ensures high display quality.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages and features of the presentinvention will be more apparent from the following description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a plan view showing the structure of an end portion of awiring substrate according to a first embodiment of the presentinvention;

FIG. 2 is a side view showing the structure of a liquid crystal displaypanel taken along the line A-A′ of FIG. 1;

FIG. 3 is a side view showing the liquid crystal display panel takenalong the line B-B′ of FIG. 1;

FIG. 4 is a plan view showing the structure of an end portion of awiring substrate according to a second embodiment of the presentinvention;

FIG. 5 is a side view showing the structure of a liquid crystal displaypanel taken along the line C-C′ of FIG. 4;

FIG. 6 is a side view showing the structure of a liquid crystal displaypanel taken along the line D-D′ of FIG. 4;

FIG. 7 is a plan view showing the structure of an end portion of awiring substrate according to a third embodiment of the presentinvention;

FIG. 8 is a side view showing the structure of a liquid crystal displaypanel taken along the line E-E′ of FIG. 7;

FIG. 9 is a plan view showing the structure of an end portion of thewiring substrate according to the fourth embodiment of the presentinvention;

FIG. 10 is a side view showing the structure of a liquid crystal displaypanel taken along the line F-F′ of FIG. 9;

FIG. 11 is a plan view showing the structure of an end portion of thewiring substrate according to the fifth embodiment of the presentinvention;

FIG. 12 is a side view showing the structure of a liquid crystal displaypanel taken along the line G-G′ of FIG. 11;

FIG. 13 is a plan view showing a corner portion of a peripheral portionof an image display portion of a TFT array substrate used in aconventional liquid crystal display device; and

FIG. 14 is a sectional view showing the structure of the conventionalliquid crystal display device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be now described herein with reference toillustrative embodiments. Those skilled in the art will recognize thatmany alternative embodiments can be accomplished using the teachings ofthe present invention and that the invention is not limited to theembodiments illustrated for explanatory purposed.

Hereinafter, embodiments of the present invention are described. Thefollowing description is given for illustrating the embodiments of thepresent invention, and the present invention is not limited to thefollowing embodiments. For clear description, the following descriptionis omitted and simplified as appropriate. Those skilled in the art couldeasily execute change, addition, and replacement of elements in thefollowing embodiments within the scope of the present invention.Incidentally, the same components are denoted by like reference numeralsthroughout the accompanying drawings, and description thereof is omittedif not necessary.

First Embodiment

Referring to FIGS. 1 to 3, a liquid crystal display device according toa first embodiment is described. FIG. 1 is a plan view showing thestructure of an end portion of a wiring substrate used in the liquidcrystal display device of this embodiment. Incidentally, FIG. 1 showsthe structure of a lower-right corner portion of a sealing member formedon the wiring substrate. FIG. 2 is a sectional view showing thestructure of a liquid crystal display panel taken along the line A-A′ ofFIG. 1. FIG. 3 is a sectional view showing the structure of the liquidcrystal display panel taken along the line B-B′ of FIG. 1. In FIGS. 1 to3, reference numeral 1 denotes a wiring substrate; 2, a display area; 3,a scanning signal line; 4, a scanning signal lead-out line connectedwith the scanning signal line; 5, a display signal line; 6, a displaysignal lead-out line connected with the display signal line; 7, a commonsignal line; 8, a sealing member; 9, a counter electrode; 10, a gateinsulating film; 11, an interlayer insulating film; 12, liquid crystal;20, an opposing substrate; 21, a driving IC; and 22, a frame area.

This embodiment describes an active matrix type liquid crystal displaydevice by way of example. That is, the wiring substrate 1 of the liquidcrystal display device of this embodiment is a TFT (thin filmtransistor) array substrate. For example, on the rectangular wiringsubstrate 1, the plural scanning signal lines 3 are formed in parallel.In FIG. 1, the plural scanning signal lines 3 are arranged in ahorizontal direction at regular pitches. The plural display signal lines5 and the plural scanning signal lines 3 cross each other with the gateinsulating film interposed therebetween. That is, the display signallines 5 are arranged on the gate insulating film 10 that covers thescanning signal lines 3, and the display signal lines 5 are formedorthogonally to the scanning signal lines 3. In FIG. 1, the pluraldisplay signal lines 5 are arranged in a vertical direction at regularpitches. The wiring substrate 1 may be a transparent insulatingsubstrate such as a glass substrate. The scanning signal line 3 and thedisplay signal line 5 have substantially the same film thickness. Thegate insulating film 10 may be, for example, a silicon oxide film orsilicon nitride film.

Thin film transistors 30 as switching elements are formed at crossingpoints between the scanning signal lines 3 and the display signal lines5. The TFT 30 includes a drain electrode and a source electrode formedusing the same layer as that for the display signal line 5. The sourceelectrode is connected with the drain electrode through a semiconductorlayer. Through the TFT, the display signal line 5 is connected with apixel electrode. Thus, a display voltage is applied from the displaysignal line 5 to the pixel electrode 13 by turning on the TFT 30. Theinterlayer insulating film 11 is formed between the pixel electrode andthe display signal line 5. Then, the drain electrode of the TFT isconnected with the pixel electrode through a contact hole formed in theinterlayer insulating film 11. The pixel electrodes are arrayed. Aportion provided with each pixel electrode is defined as a pixel. Aregion having plural pixels arrayed is defined as the display area 2.The display area 2 is formed into a rectangular shape. The frame area 22surrounds the display area 2. That is, an inner portion (upper-leftside) across the dotted line of FIG. 1 is the display area 2, and anouter portion (lower-right side) across the dotted line is the framearea 22. Incidentally, the interlayer insulating film 11 may be formedusing, for example, a silicon oxide film or silicon nitride film, or anorganic insulating film.

The frame area 22 surrounds the display area 2. That is, the frame area22 is formed in substantially hollow square shape. In the frame area 22of the wiring substrate 1, the driving IC 21 is implemented. The drivingIC 21 is provided near the lower end of the wiring substrate 1. Thedriving IC 21 serves as both a scanning signal driver IC and a displaysignal driver IC. That is, the driving IC 21 outputs a scanning signaland a display signal. Accordingly, the driving IC 21 is connected withthe scanning signal lead-out line 4 connected with the scanning signalline and the display signal lead-out line 6 connected with the displaysignal line 5.

Formed in the frame area 22 are the plural display signal lead-out lines6. The plural display signal lead-out lines 6 are arranged atpredetermined intervals not to be electrically continuous to an adjacentline. The display signal lead-out line 6 extends from the driving IC 21to the lower end of the display area 2. The display signal lead-out line6 is connected with the display signal line 5 at the lower end of thedisplay area 2. A display signal sent from the driving IC 21 is input tothe display signal line 5 through the display signal lead-out line 6.The display signal lead-out line 6 and the display signal line 5 areformed using the same conductive layer. That is, the display signallead-out line 6 and the display signal line 5 are integrally patterned.Incidentally, lines near the driving IC 21 are omitted from FIG. 1.

The scanning signal lead-out line 4 is arranged outside the lower-rightcorner of the display area 2 to extend from the driving IC 21 to thelower end of the display area 2. Then, the plural scanning signal lines3 and the plural scanning signal lead-out lines 4 provided in thedisplay area 2 are connected with each other. That is, a scanning signalfrom the driving IC 21 is input to the scanning signal line 3 throughthe scanning signal lead-out line 4. The plural scanning signal lead-outlines 4 are provided at predetermined intervals not to be electricallycontinuous to an adjacent line. The scanning signal line 3 and thescanning signal lead-out line 4 are formed using, for example, the sameconductive layer. That is, the scanning signal lead-out line 4 and thescanning signal line 3 are integrally patterned. The plural scanningsignal lead-out lines 4 provided in the frame area 22 are connected withthe scanning signal lines 3 in the order from the lower end of thedisplay area 2. In other words, the scanning signal line 3 closest tothe lower end of the display area 2 is connected with the scanningsignal lead-out line 4 closest to the display area, that is, theleftmost scanning signal lead-out line 4 at the line A-A′. The number ofscanning signal lead-out lines 4 is smaller at an upper portion of theframe area 22. Accordingly, a proportion of the scanning signal lead-outlines 4 in the frame area 22 is smaller at an upper portion of thewiring substrate 1. Hence, in the frame area 22 on the right side of thewiring substrate 1, a region having no scanning signal lead-out line 4becomes wider at an upper portion.

The common signal line 7 is provided outside the scanning signallead-out line 4. The common signal line 7 is formed in the frame area22. In other words, the scanning signal lead-out line 4 extends betweenthe common signal line 7 and the display area 2. As shown in FIGS. 2 and3, the common signal line 7 has two layers: a common signal line 7 a anda common signal line 7 b. The common signal line 7 a is formed using theconductive layer for the scanning signal lead-out line 4, and the commonsignal line 7 b is formed using the conductive layer for the displaysignal lead-out line 6. Accordingly, the common signal line 7 a isformed using a material for the scanning signal line 3 and the scanningsignal lead-out line 4 with the same film thickness as those of thescanning signal line 3 and the scanning signal lead-out line 4. Further,the common signal line 7 b is formed using a material for the displaysignal line 5 and the display signal lead-out line 6 with the same filmthickness as those of the display signal line and the display signallead-out line 6. The common signal line 7 receives a common signal fromthe driving IC 21.

Further, the gate insulating film 10 is formed between the common signalline 7 a and the common signal line 7 b. That is, the common signal line7 b is formed above the gate insulating film 10 that covers the commonsignal line 7 a. A contact hole (not shown) is formed in the gateinsulating film 10 for connecting the common signal line 7 a and thecommon signal line 7 b at the end of the wiring substrate 1. Through thecontact hole, the common signal line 7 a and the common signal line 7 bare connected. The contact hole is formed on the signal input side, thatis, near the driving IC 21. In this way, the common signal line 7 has atwo-layer structure having the common signal line 7 a and the commonsignal line 7 b, and the common signal line 7 a and the common signalline 7 b are separated by the gate insulating film 10. Thus, aresistance of the common signal line 7 can be lowered. Preferably, thecommon signal line 7 a and the scanning signal line are formed using thesame conductive layer, and the common signal line 7 b and the displaysignal line 5 are formed using the same conductive layer. Thus, thetotal thickness of the common signal line 7 can be increased, and awiring resistance of the common signal line 7 can be lowered. Inaddition, the interlayer insulating film 11 is formed above the commonsignal line 7 b.

The common signal line 7 is formed to change its pattern width. To bespecific, as shown in FIG. 1, the common signal line 7 is formed toincrease a pattern width as the distance from the driving IC 21increases. Accordingly, as shown in FIGS. 2 and 3, the pattern width ofthe common signal line 7 is different between the section taken alongthe line A-A′ of FIG. 1 and the section taken along the line B-B′ ofFIG. 1. That is, in the frame area 22 on the right side of the wiringsubstrate 1, a region having no scanning signal lead-out line 4 becomeswider at the upper end. Thus, at the upper end of the wiring substrate1, the pattern width of the common signal line 7 can become wider. Thatis, at the upper end of the wiring substrate 1, the pattern width of thecommon signal line 7 can be increased without bringing the common signalline 7 and the scanning signal lead-out line 4 into contact with eachother. In the frame area 22, the pattern width of the common signal line7 is narrower near the end portion on the side where the driving IC 21is provided and is wider near the end portion on the opposite side tothe side where the driving IC 21 is provided. As mentioned above, thepattern width of the common signal line 7 becomes wider as the distancefrom the end portion on the signal supplying side of the wiringsubstrate 1 increases.

In this embodiment, each time the scanning signal lead-out line 4 isconnected with the scanning signal line 3, the pattern width of thecommon signal line 7 is increased stepwise. That is, when the scanningsignal line 3 is connected with the scanning signal lead-out line 4, aproportion of the scanning signal lead-out line 4 in the frame area 22becomes small. Accordingly, the pattern width of the common signal line7 can be increased by an amount corresponding to the line pitch of thescanning signal lead-out line 4. In this way, a resistance of the commonsignal line 7 can be further lowered by changing the pattern width ofthe common signal line 7. Thus, a delay of the common signal can beminimized, and the display quality can be improved. Accordingly,high-speed driving is enabled without deteriorating the display quality.According to the present invention, in addition to a beneficial effectof the two-layer structure of the common signal line 7, an effect of thewider pattern width of the common signal line 7 can be produced, and aresistance of the common signal line 7 can be further lowered.

The sealing member 8 for bonding the wiring substrate 1 to the opposingsubstrate 20 is applied to the frame area 22. In general, after thesealing member 8 is applied onto the frame area 22 of the opposingsubstrate 20, the opposing substrate 20 and the wiring substrate 1 arebonded. The sealing member 8 is provided on the interlayer insulatingfilm 11. Thus, the sealing member 8 formed in the frame area 22 ispositioned above the common signal line 7. That is, as shown in FIG. 2,the sealing member 8 is formed above the common signal line 7 throughthe interlayer insulating film 11. The sealing member 8 is formed like aframe so as to surround the display area 2. The common signal line 7 andthe scanning signal lead-out line 4 are partially arranged below thesealing member 8 pattern. In this example, the common signal line 7overlaps with the right side portion of the frame-like sealing member 8.Further, the common signal line 7 extends along the right side portionof the frame-like sealing member 8. Accordingly, the common signal line7 below the sealing member 8 pattern is formed to extend in theextending direction of the right side portion of the frame-like sealingmember 8. That is, the common signal line 7 extends in the verticaldirection of FIG. 1. Accordingly, at a lower-right corner portion andthe right side portion of the frame-like sealing member 8, the sealingmember 8 overlaps with the common signal line 7.

Here, the common signal line 7 has a laminate structure including thecommon signal line 7 a and the common signal line 7 b. Therefore, thebase portion having the common signal line 7 has a larger height thanthat of the base portion having the scanning signal lead-out line 4.That is, in a region having the common signal line 7, two conductivelayers and two insulating layers are formed, and in a region having thescanning signal lead-out line 4, one conductive layer and two insulatinglayers are formed. Accordingly, the height of the base portion below thesealing member 8 pattern is increased by the film thickness of thecommon signal line 7 b in the region having the common signal line 7.

In the region having the sealing member 8 pattern, an area of thescanning signal lead-out line 4 and an area of the common signal line 7are changed stepwise. More specifically, at the lower end of the framearea 22, the region of the scanning signal lead-out line 4 becomeswider, and the region of the common signal line 7 becomes narrower. Onthe other hand, at the upper end of the frame area 22, the region of thescanning signal lead-out line 4 becomes narrower, and the region of thecommon signal line 7 becomes wider. Here, the width of the region of thescanning signal lead-out line 4 in the region having the sealing member8 pattern implies the distance between the scanning signal lead-out line4 closest to the display area and the outermost scanning signal lead-outline 4 in the region having the sealing member 8 pattern. The sum of thewidth of the region of the scanning signal lead-out line 4 and the widthof the region of the common signal line 7 can be substantially constant.The base portion below the sealing member 8 pattern gradually changesits height. That is, the base portion height is larger by the commonsignal line 7 b in the region of the common signal line 7 than in theregion of the scanning signal lead-out line 4. In this embodiment, asthe width of the scanning signal lead-out line 4 is decreased, the widthof the region of the common signal line 7 is increased stepwise. Thus,as the distance from the driving IC 21 increases, an area of the baseportion having the larger height gradually increases. Almost all thescanning signal lead-out lines 4 are connected with the scanning signallines 3 at the end portion on the opposite side to the side where thedriving IC 21 is provided, so almost all of the base portion below thesealing member 8 pattern has the larger height.

With the above pattern shape, the base portion just below the sealingmember 8 can gradually change its height. That is, the pattern width ofthe common signal line 7 gradually changes below the sealing member 8pattern such that the boundary line between the region of the commonsignal line 7 and the region of the scanning signal lead-out line 4gradually approaches the display area 2 as the distance from the drivingIC 21 increases. Further, the boundary line between a region having oneconductive layer and a region having two conductive layers can be madelonger. Thus, it is possible to suppress a luminance change accompanyingthe change in gap thickness of the portion below the sealing member 8down to a practically invisible level.

Further, almost all region of the common signal line 7 is formed belowthe sealing member 8 pattern, making it possible to suppress theinfiltration of water from the outside of the panel. That is, thepattern width of the common signal line 7 is defined such that thecommon signal line 7 is formed closer to the display area, inside theouter edge of the sealing member 8. As a result, the common signal line7 is arranged inside the outer edge of the sealing member 8 pattern.This enables an anti-corrosion liquid crystal display device. Thus, thedegradation of display quality in the liquid crystal display device canbe avoided, and the display quality of the liquid crystal display devicecan be improved. Further, with the above structure, an increase in theframe area 22 area is prevented, so a frame of the liquid crystaldisplay device can be made narrow.

Further, the common signal line 7 a and the common signal line 7 b areconnected, for example, near the corner portion of the wiring substrate1. That is, a contact hole is formed in the gate insulating film 10 forconnecting the common signal line 7 a and the common signal line 7 bnear the corner portion of the wiring substrate 1. Furthermore, theinterlayer insulating film 11 is partially removed to expose the commonsignal line 7 b. For example, a transfer electrode is formed in theregion where the common signal line 7 b is exposed. This transferelectrode makes the common signal line 7 electrically continuous to thecounter electrode 9 on the opposing substrate 20. The transfer electrodecan be formed anywhere but the portion below the sealing member 8pattern. The common signal line 7 may extend up to the end portionopposite to the end portion where the driving IC 21 is provided, and thetransfer electrode may be formed there.

The opposing substrate 20 is a transparent insulating substrate such asa glass substrate. In a color liquid crystal display device, not-showncolor filters or black matrix (BM) are formed in matrix on the opposingsubstrate 20. On the color filter or BM, the counter electrode 9opposing the pixel electrode is formed on substantially the entiresurface of the opposing substrate 20. The counter electrode 9 isconnected with the above transfer electrode.

The liquid crystal 12 is sandwiched between the opposing substrate 20and the wiring substrate 1. That is, the liquid crystal 12 is filled ina space defined between the wiring substrate 1 and the opposingsubstrate 20 and the sealing member 8. In this way, the liquid crystaldisplay panel is completed. Further, a spacer (not shown) for keeping aninterval between the wiring substrate 1 and the opposing substrate 20uniform may be provided. A backlight unit is disposed on the rear sideof the liquid crystal display panel. The backlight unit is a surfacelight source for uniformly emitting light throughout the surface. Thebacklight unit includes a light source such as an LED or a fluorescenttube, a light guide plate for guiding the light from the light source tothe entire surface, and an optical sheet such as a light diffusion sheetor a prism sheet. Further, an external control circuit is connected withthe wiring substrate 1 through, for example, a flexible wiringsubstrate. Based on a power supply voltage, control signals, and imagedata from the external control circuit, the driving IC 21 sends adisplay signal, a scanning signal, and a common signal. Then, liquidcrystal is driven by applying a voltage between the counter electrode 9and pixel electrode. As a result, an amount of light transmitted throughthe liquid crystal display panel is controlled. Incidentally, anorientation film may be provided to the wiring substrate 1 and theopposing substrate 20. Further, a polarization film may be bonded to theliquid crystal display panel.

Incidentally, the above description is directed to an example where thepattern width of the common signal line 7 is changed stepwise, but thepresent invention is not limited thereto. For example, the pattern widthof the common signal line 7 may be changed at predetermined angle. Thatis, the common signal lines 7 may be diagonally patterned. Further, inthe above description, the common signal line 7 is adjacent to thescanning signal lead-out line 4, but the present invention is notlimited thereto. For example, the common signal line 7 may be arrangedadjacent to the display signal lead-out line 6. In this case, thepattern width of the display signal lead-out line 6 is changed inaccordance with the connection between the display signal lead-out line6 and the display signal line 5. As described above, the arrangement ofthe common signal lines 7 may be appropriately changed in accordancewith the position of the driving IC 21 or the arrangement of thelead-out lines. That is, in the direction in which the common signalline 7 extends, the pattern width of the common signal line 7 aincreases as a distance from the end portion on a signal supply side ofthe wiring substrate. The display signal or the scanning signal inputfrom the signal supply side of the wiring substrate. In addition, thecommon signal line 7 may be made up of three or more conductive layersin accordance with the pattern structure of the wiring substrate 1.

In the above description, the driving IC 21 is connected onto the wiringsubstrate 1, but the present invention is not limited thereto. Forexample, the driving IC may be provided outside the wiring substrate 1,and a flexible wiring substrate (FPC) may be connected with the wiringsubstrate 1. In this case, the driving IC 21 provided outside the wiringsubstrate 1 supplies signals through the FPC. This structure alsoproduces the same beneficial effects as the above effects.

Second Embodiment

Referring to FIGS. 4 to 6, the structure of a liquid crystal displaydevice according to a second embodiment of the present invention isdescribed. FIG. 4 is a plan view showing the structure of an end portionof a wiring substrate used in the liquid crystal display device of thisembodiment. Incidentally, FIG. 4 shows the structure of the lower-rightcorner portion of the sealing member in the wiring substrate. FIG. 5 isa sectional view showing the structure of the liquid crystal displaypanel taken along the line C-C′ of FIG. 4. FIG. 6 is a sectional viewshowing the structure of the liquid crystal display panel taken alongthe line D-D′ of FIG. 4. The basic structure of the wiring substrate ofthis embodiment is the same as the first embodiment, so detaileddescription thereof is omitted. Further, description about the samecomponents as those of the first embodiment is omitted.

In this embodiment, the scanning signal lead-out line 4 is formed insidethe pattern of the sealing member 8. In addition, the common signal line7 is provided outside the plural scanning lead-out lines 4. Further,only the pattern width of the common signal line 7 b of the commonsignal line 7 having the two-layer structure is changed below the rightside portion of frame-like sealing member. That is, the pattern width ofthe common signal line 7 a of the common signal line 7 having thetwo-layer structure is substantially uniform below the sealing member 8of the frame area 22 at the right end. More specifically, as shown inFIG. 5, the pattern width of the common signal line 7 b is much smallerthan that of the common signal line 7 a near the driving IC 21. Thepattern width of the common signal line 7 b increases as the distancefrom the driving IC 21 increases. Then, as the distance from the drivingIC 21 is further increased, the pattern width of the common signal line7 b is set to a predetermined width. Here, as shown in FIG. 6, thepattern width of the common signal line 7 b is larger than that of thecommon signal line 7 a. That is, the pattern width of the common signalline 7 b of the common signal line 7 extending along the right sideportion of the frame-like sealing member 8 gradually increases as thedistance from the driving IC increases.

As shown in FIG. 4, the common signal lines 7 b are diagonally patternedat the lower-right corner portion of the sealing member 8. Accordingly,as shown in FIG. 5, the pattern width of the common signal line 7 b issmaller than that of the common signal line 7 a in the section takenalong the line C-C′ near the driving IC 21. Then, in the section takenalong the line D-D′ apart from the driving IC 21, as shown in FIG. 6,the pattern width of the common signal line 7 b is larger. Thus, aneffective line width of the common signal line 7 can be increased, and aline resistance can be lowered. Incidentally, if the pattern width ofthe common signal line 7 b is increased to extend up to the inside ofthe pattern of the sealing member 8, the pattern width is set constanteven if the distance from the driving IC 21 increases. Here, the commonsignal line 7 a and the common signal line 7 b are connected through thecontact hole provided on the driving IC 21 side. The contact hole can beformed near the line C-C′. At this time, if the contact hole is smallenough, an influence of the panel gap is suppressed down to an invisiblelevel. Alternatively, the common signal line 7 b partially extends to aportion near the driving IC 21, and the contact hole may be formedoutside the sealing member 8. In this case, the common signal line 7 bextends to the outside of the sealing member 8 on the driving IC 21side. That is, the pattern of the common signal line 7 b is formed abovea part of the pattern of the common signal line 7 a. The pattern of thecommon signal line 7 b preferably extends on the opposite side to theside adjacent to the scanning signal lead-out line 4. That is, thepattern of the common signal line 7 b preferably extends along the outeredge of the sealing member 8.

Further, the common signal line 7 formed near the scanning signallead-out line 4 below the sealing member 8 is made up of one conductivelayer. That is, the common signal line 7 b is not formed in the vicinityof the scanning signal lead-out line 4. In the region having thescanning signal lead-out line 4, one conductive layer and two insulatingfilms are formed. The common signal line 7 near the scanning signallead-out line 4 below the sealing member 8 includes one conductive layerand two insulating films. Accordingly, in a region having the sealingmember 8 pattern, the region of the common signal line 7 and the regionof the scanning signal lead-out line 4 have one conductive layer at thevicinity of the boundary therebetween. Thus, the abrupt change in heightof the base portion is controlled. Hence, it is possible to prevent theuneven display caused at the boundary between the region of the commonsignal line 7 and the region of the scanning signal lead-out line 4.

Further, in this embodiment, the common signal lines 7 b are diagonallypatterned. Thus, in the direction in which the common signal line 7extends, the boundary line between the region having one conductivelayer and the region having two conductive layers is graduallyapproaching the display area. That is, in the region where the sealingmember 8 overlaps with the common signal line 7, a ratio in widthbetween the region including two or more conductive layers and theregion including only one conductive layer is made to successivelyincrease. As a result, in the region having the common signal line 7,the abrupt change in height of the sealing member 8 is suppressed. Inthis way, the uneven display due to the change in height of the baseportion below the sealing member 8 can be controlled. Further, most ofthe common signal line 7 underlies the pattern of the sealing member 8to thereby suppress the infiltration of water or the like from theoutside of the panel. That is, the pattern width of the common signalline 7 is determined such that the common signal line 7 is providedinside the outer edge of the sealing member 8. Thus, the anti-corrosiondisplay device can be provided, and the reduction in display quality ofthe liquid crystal display device can be prevented. Accordingly, thedisplay quality of the liquid crystal display device can be improved.

In this embodiment, a beneficial effect can be obtained due to themulti-layer structure of the common signal line 7, and a resistance canbe lowered. The above example describes the case where the common signalline 7 has the two-layer structure, but the common signal line 7 mayhave the multi-layer structure of three or more layers. In addition, inthe portion where the sealing member 8 overlaps with the common signalline 7, the height of the base portion below the sealing member 8 can begradually changed. Thus, the luminance change accompanying the change ingap below the sealing member 8 can be suppressed down to a practicallynegligible level. Further, most of the common signal line 7 underliesthe sealing member to thereby suppress the infiltration of water or thelike from the outside of the panel and provide the anti-corrosion liquidcrystal display device. With the above structure, it is possible to keepthe frame area 22 small and downsize the liquid crystal display device.

In the illustrated example of FIG. 4, the common signal lines 7 b arediagonally patterned, but the present invention is not limited thereto.For example, similar to the first embodiment, the pattern width of thecommon signal line 7 b may be changed stepwise. Further, in the aboveexample, the common signal line 7 is adjacent to the scanning signallead-out line 4 below the sealing member 8, but similar beneficialeffects can be attained with the structure where the common signal line7 is adjacent to the display signal lead-out line 6. In this case, thepattern width of the common signal line 7 a made up of a conductivelayer used for the scanning lead-out line 4 may be changed.

Preferably, the common signal line 7 a and the scanning signal line areformed using the same conductive layer, and the common signal line 7 band the display signal line 5 are formed using the same conductivelayer. The scanning signal line 3 and the display signal line 5 arepatterned in different photolithographic steps, so the common signalline 7 a and the common signal line 7 b may have different patterns.Thus, a resistance of the common signal line can be lowered due to anincrease in line width and line thickness. Further, a drop inproductivity due to the increase in the number of manufacturingprocesses can be avoided.

Third Embodiment

Referring to FIGS. 7 and 8, the structure of a liquid crystal displaydevice according to a third embodiment of the present invention isdescribed. FIG. 7 is a plan view showing the structure of an end portionof a wiring substrate used in the liquid crystal display device of thisembodiment. Incidentally, in FIG. 7, the structure of the lower-rightcorner portion of the sealing member in the wiring substrate isdemonstrated. FIG. 8 is a sectional view showing the structure of theliquid crystal display panel taken along the line E-E′ of FIG. 7.Incidentally, the basic structure of the wiring substrate of thisembodiment is the same as that of the first embodiment, so detaileddescription thereof is omitted. Furthermore, description about the samecomponents as those of the first embodiment is omitted.

In this embodiment, the pattern shape of the common signal line 7provided outside the scanning signal lead-out line 4 is the same as thatof the first embodiment. Further, in this embodiment, a common signalauxiliary line 17 extends between adjacent scanning signal lead-outlines. The common signal auxiliary line 17 is formed in a positioncorresponding to a gap between the adjacent the scanning signal lead-outlines 4. The line patterns of the common signal auxiliary lines 17 andthe line patterns of the scanning signal lead-out lines 4 arealternately arranged.

The common signal auxiliary line 17 and the display signal line 5 areformed using the same conductive layer. That is, common signal auxiliaryline 17 and the common signal line 7 b are formed with the same materialand thickness. As shown in FIG. 8, the scanning signal lead-out line 4is not formed below the common signal auxiliary line 17. Thus, theheight of the base portion below the sealing member 8 is based on oneconductive layer and two insulating layers inside the common signal line7. That is, the base portion height is the sum of the film thicknessesof the interlayer insulating film 11 and the gate insulating film 10 andthe film thickness of the display signal line 5 or the scanning signalline 3. In general, the thickness of scanning signal line 3 is notlargely different from that of the display signal line 5. Accordingly,in the region having the scanning signal lead-out line 4, the height ofthe base portion below the sealing member 8 pattern can be madesubstantially uniform.

The plural common signal auxiliary lines 17 are connected with commonsignal connecting lines 27 provided below the sealing member 8. Thecommon signal connecting lines 27 and the common signal auxiliary line17 can be formed using the same conductive layer. The common signalauxiliary line 17 and the common signal connecting lines 27 areconnected with the driving IC 21, and supplied with common signals.

In this way, the common signal auxiliary line 17 is formed between thescanning signal lead-out lines 4, whereby the number of signal paths canbe increased, and an effective line width of the common signal line 7can be increased. Thus, a line resistance can be lowered, and thedisplay quality can be improved.

If the common signal auxiliary line 17 and the scanning signal lead-outline 4 are formed using different conductive layers, the lines areprevented from short-circuiting even in the case of setting a relativelylarge pattern pitch in the same layer. That is, a line resistance can befurther reduced without short-circuiting the lines.

In the above example, the common signal auxiliary line 17 extendsbetween the scanning signal lead-out lines 4, but the present inventionis not limited thereto. For example, the common signal auxiliary line 17may be formed between the display signal lead-out lines 6. In this case,the common signal auxiliary line 17, and the scanning signal line 3 andthe scanning signal lead-out line 4 are formed using the same conductivelayer. Further, instead of adding the common signal auxiliary line 17 tothe structure of the first embodiment, the common signal auxiliary line17 may be used solely. That is, in the structure where the pattern widthof the common signal line 7 is set substantially uniform, the commonsignal auxiliary line 17 and the common signal connecting lines 27 maybe provided. Further, the common signal auxiliary line 17 may be uses tothe embodiment 2. That is, this embodiment may be applied to theembodiment 2.

Fourth Embodiment

Referring to FIGS. 9 and 10, the structure of a liquid crystal displaydevice according to a fourth embodiment of the present invention isdescribed. FIG. 9 is a plan view showing the structure of an end portionof a wiring substrate used in the liquid crystal display device of thisembodiment. Incidentally, FIG. 9 shows the structure of the lower-rightcorner portion of the sealing member 8 in the wiring substrate. FIG. 10is a sectional view showing the structure of the liquid crystal displaypanel taken along the line F-F′ of FIG. 9. Incidentally, the basicstructure of the wiring substrate of this embodiment is the same as thatof the first embodiment, so detailed description thereof is omitted.Further, description about the same components as those of the firstembodiment is omitted.

In this embodiment, the interlayer insulating film 11 on the wiringsubstrate 11 is an organic insulating film. That is, the interlayerinsulating film 11 as the organic insulating film is formed above thedisplay signal line 5 and the scanning signal line 3. The pixelelectrode 13 is formed on the interlayer insulating film 11. In thisembodiment, the pattern of the common signal line 7 b is formedconcurrently with the formation of the pixel electrode 13. That is, thecommon signal line 7 b and the pixel electrode 13 are formed using thesame conductive layer. Accordingly, the common signal line 7 has thetwo-layer structure: the conductive layer used for the scanning signalline 3 and the conductive layer used for the pixel electrode 13. Thus, aline resistance of the common signal line 7 can be lowered.

In the wiring substrate 1, the surfaces of the scanning signal line 3and the display signal line 5, and the lead-out lines 4 and 6 areleveled independently of the influence of the base portion pattern dueto the effects of the interlayer insulating film 11. That is, thethickness of the organic insulating film is generally much larger thanthat of inorganic metal thin films forming each line. Accordingly, theinfluence of the line pattern of the base portion can be suppressed byforming the interlayer insulating film 11 as the organic insulatingfilm. A change in cell gap due to the difference in height between thepattern formation region of the lead-out lines 4 and 6 of the scanningsignal line 3 or the display signal line 5 and the formation region ofthe common signal line 7 is negligible.

Incidentally, the difference in level in the display area 2 on theinterlayer insulating film 11 due to the pixel electrode 13 may cause adifference in cell gap around the display area. This is more conspicuousin the liquid crystal display device having the thick pixel electrode13, for example, a reflection-type liquid crystal display device. Thatis, in the reflection-type liquid crystal display device, a metal thinfilm thicker than a transparent conductive film is used for the pixelelectrode. In this case, as shown in FIG. 10, the common signal line 7 bbelow the sealing member 8 pattern and the pixel electrode 13 of thedisplay area 2 are formed using the same conductive layer. Thus, thechange in panel gap in the region having the display area 2 and thesealing member 8 can be suppressed. Further, the common signal line 7has the laminate structure, and a resistance can be lowered.

Incidentally, in this embodiment, the common signal line 7 has thetwo-layer structure: the conductive layer used for the scanning signalline 3 and the conductive layer used for the pixel electrode 13, but thepresent invention is not limited thereto. For example, the common signalline 7 may have the two-layer structure: the conductive layer used forthe pixel electrode 13 and the conductive layer used for the displaysignal line 5. The common signal line 7 preferably has the two-layerstructure: the conductive layer used for a lead-out line adjacent to thecommon signal line 7 pattern and the conductive layer used for the pixelelectrode. Needless to say, the common signal line 7 may have thelaminate structure of three or more layers. Further, the pixel electrode13 and the organic insulating film shown in this embodiment may be usesto the embodiment 2, 3. That is, this embodiment may be applied to theembodiment 2, 3.

Fifth Embodiment

Referring to FIGS. 11 and 12, the structure of a liquid crystal displaydevice according to a fifth embodiment of the present invention isdescribed. FIG. 11 is a plan view showing the structure of an endportion of a wiring substrate used in the liquid crystal display deviceof this embodiment. Incidentally, FIG. 11 shows the structure of thelower-right corner portion of the display area 2 in the wiringsubstrate. FIG. 12 is a sectional view showing the structure of theliquid crystal display panel taken along the line G-G′ of FIG. 11. Thebasic structure of the wiring substrate of this embodiment is the sameas the first embodiment, so detailed description thereof is omitted.Further, description about the same components as those of the firstembodiment is omitted.

In this embodiment, at one side of the sealing member 8 where the commonsignal line 7 extends, the common signal line 7 a as the lower one ofthe two layers of the common signal line 7 extends to the outside of theouter edge of the sealing member 8 pattern. More specifically, thecommon signal line 7 a and the common signal line 7 b are formed withdifferent pattern widths. Then, the common signal line 7 a, not theuppermost common signal line 7 b, is arranged on the substrate edgeoutside the pattern outer edge of the sealing member 8. Then, the gateinsulating film 10 and the interlayer insulating film 11 are formed onthe common signal line 7 a. Thus, a portion of the common signal line 7a protruding from the outer edge of the sealing member 8 pattern may becovered with two insulating films. Accordingly, if one insulating filmis damaged due to a pin-hole or foreign substance, the other insulatingfilm protects the common signal line 7 a, so practically high corrosionresistance is ensured. Further, the line width can be substantiallyincreases, so a resistance of the common signal line 7 can be lowered.Further, the common signal line 7 extending to the outside of the outeredge of the sealing member 8 pattern and two insulating films coveringthe common signal line shown in this embodiment may be uses to theembodiment 2, 3, 4. That is, this embodiment may be applied to theembodiment 2, 3, 4.

The lines of the first to fifth embodiments are formed using metal thinfilms such as Al or Cr film. Needless to say, the other materials may beused. For example, the metal thin film is formed through sputtering orvacuum evaporation, and patterned through photolithography, whereby theline patterns can be formed. Further, the pixel electrode 13 and thecounter electrode 9 are made up of a transparent conductive film such asan ITO film. For example, the transparent conductive film is formedthrough sputtering or vacuum evaporation, and patterned throughphotolithography, whereby the pixel electrode 13 and the counterelectrode 9 can be formed. Incidentally, if the counter electrode 9 isformed on the entire surface of the opposing substrate, patterningthrough the photolithography is unnecessary. Further, in the case of thereflection type liquid crystal display device, the pixel electrode ismade up of a metal thin film. The same conductive layers as the wiringlayers are laminated to form the common signal line 7, whereby thecommon signal line 7 can be patterned into a desired shape withoutincreasing the number of manufacturing processes.

The first to fifth embodiments describe the common signal line 7 formedof the two conductive layers, but the present invention is not limitedthereto. For example, the common signal line 7 may be made up of threeor more conductive layers. That is, the common signal line 7 needs onlyto have at least two conductive layers. Further, the common signal line7 is preferably made up of at least two conductive layers of conductivelayers used for the scanning signal line 3, conductive layers used forthe display signal line 5, or conductive layers used for the pixelelectrode 13.

It is apparent that the present invention is not limited to the aboveembodiment that may be modified and changed without departing from thescope and spirit of the invention.

1. A liquid crystal display device, comprising: a wiring substrate; anopposing substrate opposite to the wiring substrate; a sealing memberfor bonding the wiring substrate to the opposing substrate; a liquidcrystal filled in a space defined by the wiring substrate, the opposingsubstrate, and the sealing member, a plurality of scanning signal linesformed in a display area formed inside the sealing member; a pluralityof display signal lines formed in the display area and crossing thescanning signal lines through an insulating film; and a common signalline formed outside the display area and extending along one end of thesealing member below the pattern of the sealing member; the scanningsignal lines, the display signal lines, and common signal line beingformed on the wiring substrate, and the common signal line including atleast two conductive layers, the conductive layer that is not anuppermost conductive layer among the conductive layers of the commonsignal line extending up to the outside of an outer edge of the patternof the sealing member at one end of the sealing member in which thecommon signal line extends, the uppermost conductive layer does notextend to the outside of an outer edge of the pattern of the sealingmember at one end of the sealing member in which the common signal lineextends, and the conductive layers extending up to the outside of theouter edge of the pattern of the sealing member being covered with twoor more insulating films.
 2. The liquid crystal display device accordingto claim 1, wherein the common signal line includes a conductive layerfor forming the display signal line and a conductive layer for formingthe scanning signal line.
 3. The liquid crystal display device accordingto claim 1, wherein a pixel electrode connected with the display signalline through a switching element, and an organic insulating filmprovided below the pixel electrode are formed on the wiring substrate,the organic insulating film provided above the display signal line andthe scanning signal line, and the common signal line includes aconductive layer for forming the pixel electrode.